The objective of this research is to determine the molecular structure of ubiquitin, using protein x-ray crystallographic techniques. This nonhistone chromosomal protein, which has been sequenced and has a molecular weight of 8,451 daltons, has been crystallized in this laboratory, and work toward the low-resolution structure is in progress. The ultimate goal is the high-resolution (2.5 A) crystal structure; this structure may provide clues to the function that this molecule serves in chromatin.